The basic mechanisms responsible for development of pelvic organ prolapse (POP) are not established. It has long been hypothesize that levator ani (LA) muscle impairment is associated with POP but this hypothesis has not been tested. This case control study will test the Null Hypothesis that levator ani muscle structure and function are the same in women with pelvic organ prolapse (cases) and women with normal support (controls). We will study 150 Cases who will be women with pelvic organ prolapse that extends more than 1 cm below the hymenal ring and 150 asymptomatic Controls with proven normal support matched for age, parity and race. Women with prior treatment for POP will be excluded. Differences in LA structure and function between cases and controls will be sought. Tests of LA structure and function: Structural abnormalities in LA muscle anatomy will be quantified in high-resolution proton density MR images. LA strength will be measured at rest and during maximum muscle contraction. Aim I: Test the null hypotheses that there are no differences in the anatomical cross-sectional area of the pubovisceral portion of the LA as seen in MR images of cases and controls. Aim 2: Test the null hypothesis that there is no difference in LA muscle strength at rest or during maximal contraction function in cases compared to controls. Sub analyses of levator anatomy and strength based on the size and type of the prolapse as well as the presence or absence of stress incontinence will also be carried out. Analysis of covariates possibly contributing to prolapse including prior hysterectomy, obesity, estrogen status, heavy lifting, and prolapse family history will be performed. Aim 3: Test the null hypothesis that muscle cross-sectional area is not correlated with LA strength for either cases or controls. The importance of this research lies in its providing fundamental insights about the specific functional and anatomical defects present in women with POP that will lead to improved research in this common disease. This information will guide future research as well as helping to devising more rational treatment selection.